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The     Osmotic     Pressure     of 

Cane  Sugar  Solutions  at 

15°  Centigrade. 


DISSERTATION 


SUBMITTED   TO   THE   BOARD    OF    GRADUATE    STUDIES    OF 

THE  JOHNS   HOPKINS   UNIVERSITY  IN  CONFORMITY 

WITH  THE  REQUIREMENTS  FOR  THE  DEGREE 

OF  DOCTOR  OF  PHILOSOPHY. 


BY 


BRAINERD  MEARS. 


1908 


EASTON,  PA.  : 

ESCHENBACH  PRINTING  COMPANY. 
1908 


The     Osmotic     Pressure     of 

Cane  Sugar  Solutions  at 

15°  Centigrade. 


DISSERTATION 


SUBMITTED   TO   THE   BOARD    OF    GRADUATE    STUDIES    OF 

THE  JOHNS   HOPKINS   UNIVERSITY  IN  CONFORMITY 

WITH  THE  REQUIREMENTS  FOR  THE  DEGREE 

OF  DOCTOR  OF  PHILOSOPHY. 


BY 


BRAINERD  HEARS. 


EASTON,  PA.  : 

ESCHENBACH  PRINTING  COMPANY. 
1908 


M4- 


CONTENTS. 
Acknowledgment 


General  Discussion 

Series  I  at  15° 

Series  II  at  15° jg 

Conclusion 

A  New  Cell  for  Measurement  of  Osmotic  Pressure 

Biographical 

37 


186959 


ACKNOWLEDGMENT. 

The  author  takes  pleasure  in  expressing  his  gratitude  to 
President  Remsen,  Professor  Morse,  Professor  Jones,  Pro- 
fessor Mathews  and  Associate  Professor  Acree  for  instruction 
in  the  lecture  room  and  laboratory.  Especial  thanks  are 
due  to  Professor  Morse  under  whose  personal  direction  this 
investigation  was  carried  out  and  to  Dr.  Frazer,  Dr.  Lovelace 
and  Dr.  Holland  for  their  aid  and  personal  interest  in  the 
work. 


The  Osmotic  Pressure  of  Cane  Sugar 
Solutions  at  15°  Centigrade. 


INTRODUCTION. 

The  deviation  of  osmotic  pressure  from  that  of  gas 
pressure  in  the  vicinity  of  o°  centigrade  while  the  two  were 
found  to  be  in  close  agreement  near  20°  has  led  to  a  series 
of  measurements  at  intermediate  temperatures.  Results 
at  o0,1  5°,2  10°, 3  and  20°, 4  have  already  been  obtained  in 
this  laboratory.  The  present  investigation  has  been  carried 
out  at  15°. 

CELLS   AND   MANOMETERS. 

The  cells  designated  G,  D  and  B  were  employed  in  the 
measurements  as  they  had  been  found  to  be  especially  trust- 
worthy in  previous  work,  also  some  new  forms  of  cells  which 
will  be  described  later  in  this  dissertation.  The  manometers5 
and  other  apparatus  were  the  same  as  those  already  described 
in  connection  with  earlier  investigations.  One  improve- 
ment, however,  was  introduced.  The  brass  nuts  employed 
to  force  the  rubber  stoppers  on  the  manometers  into  the  glass 
tubes  of  the  cell  and  thus  furnish  mechanical  pressure  on  the 
cell  content,  which  had  previously  been  fixed  on  the  manom- 
eter tubes  were  slotted  in  such  a  way  that  they  could  be 
removed  at  will.  This  change  gave  a  lighter  instrument 
less  subject  to  the  danger  of  breaking  in  handling. 

DEPOSITION    OF    MEMBRANES. 

The  membranes  were  precipitated  as  usual  by  the  elec- 
trolytic method.6  Care  was  taken  in  depositing  to  keep  the 

1  Am.  Chem.  J.,  37,  425. 
z  Ibid.,  38,  175. 

3  H.  V.  Morse,  Dissertation,  1908. 

4  Am.  Chem.  Jour.,  36,  39. 
s  Ibid.,  36,  21. 

•  Ibid.,  36,  29. 


temperature  near  15°  and  thus  prevent  the  tendency  to 
stretch,  or  rupture  the  layer  of  copper  ferrocyanide  by  the 
expansion  or  contraction  of  the  cell  wall. 

PRECAUTIONS   AGAINST   DILUTION. 

To  prevent  dilution  of  the  cell  contents  due  to  the  draw- 
ing in  of  water  at  the  time  of  opening  and  closing,  all  of  the 
cells  were  dipped  in  sugar  solutions  of  o°.i  normal  higher 
concentration  than  that  in  the  interior  of  the  cell,  as  has  been 
previously  described  in  this  work.1  This  treatment,  how- 
ever while  it  has  materially  lessened  the  loss  in  rotation,  did 
not  seem  to  be  capable  of  further  refinement.  Some  advance 
along  this  line  was  imperative  as  the  loss  in  rotation  of  the 
sugar  solutions  in  the  cell  and  the  methods  of  correcting  for 
it,  whether  ascribed  to  inversion  or  to  one-half  dilution, 
appeared  to  be  the  feature  of  the  measurements  most  open 
to  criticism.  Believing  as  we  did  that  most  of  this  loss  in 
rotation  was  caused  by  dilution  and  that  it  was  due  to  sub- 
jecting the  contents  of  the  cell  to  diminished  pressure  at  some 
stage  of  the  measurement,  we  proceeded  to  investigate  the 
places  at  which  such  a  condition  could  exist.  It  seemed 
probable  that  very  little  occurred  at  the  setting  up  of  the  cell 
as  care  was  taken  at  that  time  to  keep  the  cell  contents  under 
increased  pressure  while  connecting  the  manometer  and  rubber 
stopper  with  the  glass  tube  of  the  cell.  From  this  point 
no  danger  could  arise  because  of  the  osmotic  pressure,  until 
the  operation  of  opening  the  cell  at  the  close  of  the  measure- 
ment. Here  on  withdrawing  the  manometer  some  diminished 
pressure  was  exerted  as  was  shown  by  the  fact  that  mercury 
was  often  sucked  back  into  the  cell  from  the  bulbs  of  the 
manometer.  This  had  been  previously  noted  and  was 
formerly  relieved  by  the  admission  of  air  to  the  cell  with  a 
sharp  pointed  steel  instrument  pressed  between  the  rubber 
stopper  and  the  connecting-glass  tube.  This  operation, 
however,  did  not  furnish  the  continuous  passage  necessary 
between  the  interior  of  the  cell  and  the  atmosphere  and  some 
diminished  pressure  could  be  observed  at  this  point,  Here 

1  p.  B.  Dunbar,  Dissertation,  1907, 


then,  seemed  to  be  the  place  for  improvement  in  the  method. 
Consequently,  previous  to  the  operation  of  opening  the 
cell,  the  stopper  was  pierced  by  a  small,  sharpened  steel 
tube.  A  hypodermic  needle  about  two  inches  long  was  found 
suitable.  On  penetrating  the  rubber  stopper  this  tube  at 
once  afforded  free  communication  between  the  interior  of 
the  cell  and  the  external  air,  and,  with  this  connection  es- 
tablished, the  manometer  could  be  withdrawn  without  the 
least  indication  of  diminished  pressure.  This  procedure 
seemed  to  promise  well,  but  we  were  hardly  prepared  for  the 
remarkable  improvement  which  was  immediately  experi- 
enced. By  use  of  the  needle  no  loss  in  rotation  could  be 
detected  with  the  polariscope  from  the  o.i  through  the  0.6 
normal  concentrations  and  from  this  point  on  to  the  normal 
solutions,  while  a  loss  in  rotation  was  observed  at  times. 
It  was  much  smaller  than  in  any  previous  set  of  measure- 
ments. Further,  this  loss  found  in  the  higher  concentrations 
tallied  well  with  results  obtained  in  earlier  works  where  the 
polariscope  was  not  employed,  but  the  inversion  determined 
by  means  of  Fehling's  solution.1  A  small  change  may  also 
be  accounted  for  by  the  fact  that  the  capacity  of  the  cell  may 
increase  slightly  by  the  rising  of  the  manometers  and  con- 
sequent dilution  with  water,  for  while,  by  careful  manipu- 
lation, this  defect  has  been  overcome  to  a  large  extent  and 
is  absent  in  the  lower  concentrations,  in  the  higher  where 
the  larger  pressures  are  developed,  a  rise  of  0.5  mm.  is  not 
unusual. 

CORRECTION   FOR   LOSS   IN    ROTATION. 

With  this  means  of  obtaining  somewhat  quantitative 
evidence,  we  can  proceed  to  a  more  intelligent  understanding 
of  the  causes  of  loss  in  rotation.  In  the  first  place,  it  is 
clearly  shown  that  as  a  rule,  little  or  no  change  in  the  concen- 
tration of  the  sugar  solution  takes  place  at  the  time  of  closing 
the  cell.  While  this  had  been  previously  suspected,  with 
no  exact  data  at  hand  the  best  correction  which  could  be 
applied  to  the  measurements  was  to  presuppose  that  an  equal 

1  Am.  Chem.  Jour.,  34,  1. 


8 

part  of  the  dilution  took  place  at  the  opening  and  closing  of 
the  cell,  and  as  only  the  dilution  which  takes  place  during 
the  setting  up  process  affects  the  measured  pressures,  we  were 
forced  to  determine  the  whole  loss  in  rotation  and  subtract 
one-half  of  the  result,  calculated  as  dilution  from  the  observed 
osmotic  pressure.  It  is  now  obvious  that  this  procedure 
was  incorrect.  The  change  in  rotation  observed  and  cor- 
rected for  as  one-half  dilution  was  due  to  three  causes:  first 
and  principally,  as  now  known,  to  a  dilution  at  the  time  of 
opening  the  cell  which  consequently  did  not  affect  the  pres- 
sure as  observed;  second,  to  some  inversion  beginning  at  the 
0.6  and  increasing  to  the  normal  solution;  and  third,  to  a 
small  increase  in  the  capacity  of  the  cell,  due  to  the  rising  of 
the  manometers  and  stoppers.  From  this  evidence  the  con- 
clusion follows  that  the  previous  determinations  of  osmotic 
pressure  of  cane-sugar  up  to  the  0.6  normal  concentrations 
are  accurate  without  correction  and  that  from  this  point  on 
the  results  might  be  corrected  for  inversion  whenever  loss  in 
rotation  is  observed,  and  we  have  followed  this  method  in 
the  present  measurements. 

Absolute  perfection,  however,  has  not  been  reached  in 
this  matter  of  correction  for  change  in  rotation,  for  while  it 
has  been  proved  that  practically  all  of  this  loss,  when  the 
needle  is  employed,  is  due  to  inversion  nevertheless,  as  is 
pointed  out  above,  a  trace  may  be  due  to  dilution,  and  this  at 
present  we  are  unable  to  estimate.  The  quantities  involved 
are,  however,  too  small  to  essentially  change  the  results. 

Another  advantage  was  also  found  in  the  use  of  the  needle. 
It  was  possible  to  keep  the  manometer  more  completely 
filled  with  mercury  as  it  was  not  sucked  out  at  the  time  of 
opening  the  cell.  This  fact  tended  to  prevent  the  sugar 
solution  from  working  round  between  the  glass  and  the 
mercury  and  eventually  contaminating  the  enclosed  gas. 
When  such  action  occurs  it  is  necessary  to  open  the  manom- 
eter for  cleaning  and  refilling  and  to  re-determine  the  gas 
volume,  an  operation  requiring  time  and  considerable  skill. 

After  the  closing  of  the  cell  care  must  be  taken  not  to 


subject  its  contents  to  mechanical  pressure  greater  than  the 
osmotic  pressure  exerted  by  the  solution.  Should  such 
pressure  be  applied  some  water  is  forced  out  through  the 
membrane,  causing  a  permanent  concentration  of  the  solution 
under  investigation  as  at  this  point  the  capacity  of  the  cell 
is  fixed;  consequently,  on  measuring  the  osmotic  pressure, 
abnormally  high  results  are  obtained  and  the  determination 
is  of  little  value.  This  difficulty  is  most  often  experienced  in 
the  o.i  normal  concentrations. 

MATERIAL 

The  cane-sugar  employed  was  the  best  grade  of  white 
rock  candy,  pulverized  and  dried  over  calcium  chloride  to 
constant  weight.  Two  analyses  gave  the  following  results: 

I.  II.         Theoretical. 

C  42.02  42.08  42.08 

H  6.42  6.47  6.48 

Solutions  of  this  sugar  from  the  o.  i  to  the  normal  concentra- 
tions, prepared  on  the  weight  normal  bases,  gave  identical 
rotations  with  the  solutions  of  previous  workers  at  the  same 
temperatures. 

The  results  given  in  Tables  I  to  IX  were  obtained  during 
the  months  of  April  and  May,  1907,  employing  the  cooling 
effects  of  hydrant  water  circulating  through  brass  pipes  as  a 
temperature  regulator,1  and  they  were  carried  on  until  it  was 
no  longer  possible  to  obtain  15°  in  the  bath.  We  were  obliged 
to  omit  the  o.i,  0.9  and  normal  concentrations  and  also 
several  check  experiments  on  some  of  the  other  concentrations. 
It  was  our  intention  to  complete  the  series  on  the  return  of 
cold  weather.  However,  in  the  fall  several  factors  caused  a 
change  in  the  work.  All  of  the  determinations  were  made 
with  manometers  filled  with  air  which  has  been  subsequently 
shown  to  introduce  the  objectionable  feature  of  shrinkage  in 
the  original  air  volume  and  to  necessitate  a  corresponding 
correction  of  the  observed  pressures.2  It  was  also  difficult 
to  decide  where  to  begin  to  apply  this  correction  to  the 
results.  Accordingly,  it  was  determined  to  repeat  the 

1  Am.  Chem.  Jour.,  38,  175. 

9  P.  B.  Dunbar,  Dissertation,  1907. 


IO 

measurements  with  manometers  rilled  with  nitrogen,  with 
the  hope  that  errors  from  this  source  would  be  eliminated. 
Moreover,  careful  inspection  of  osmotic  pressure  data  has 
shown  that  too  much  stress  cannot  be  laid  on  the  maintenance 
of  constant  temperatures,  not  only  in  the  bath  proper  where 
the  readings  are  taken,  but  also  in  the  solutions  and  cell  at 
the  time  of  its  closing.  Variations  of  0.1°  change  the  con- 
centration of  the  contents  of  the  cell,  due  to  sucking  in  or 
expulsion  of  water,  and  produce  thermometer  effects  or 
abnormal  pressures  requiring  three  or  four  hours  for  the  re- 
establishment  of  normal  equilibrium  conditions  which  seemed 
fatal  to  concordant  results. 

CONSTANT  TEMPERATURE    BATH. 

To  secure  more  accurate  temperature  regulation  in  the 
bath  proper,  the  cooling  device  of  brass  pipes  and  flowing 
tap  water  previously  described1  was  considerably  improved. 
There  appeared  to  be  three  defects  in  the  original  arrange- 
ment: first,  owing  to  the  varying  pressure  on  the  city 
main  it  was  found  impossible  to  obtain  a  constant  flow  of 
the  cooling  water  through  the  bath;  second,  this  water  in 
passing  through  the  bath,  necessarily  experiencing  a  rise  in 
temperature,  liberated  some  of  its  dissolved  air  which  in  time 
accumulated  to  form  air  cushions  in  the  loops  of  the  pipes 
and  eventually  tended  to  check  the  flow  of  water  completely ; 
and  third,  the  supply  of  water  after  uniform  flow  was  secured, 
varied  in  temperature  and  at  some  times  in  the  year  was  too 
warm  to  cool  the  bath  to  the  desired  point. 

The  first  of  these  objections  was  overcome  by  the  erection 
of  an  iron  standpipe  of  suitable  length  to  give  sufficient 
pressure  for  the  circulation  of  the  cooling  water  in  the  pipes 
of  the  bath.  Hydrant  water  was  admitted  to  the  base  of 
this  standpipe  through  a  valve  in  excess  of  the  amount 
required  for  cooling  so  that,  however  the  pressure  of  the  supply 
might  vary,  there  was  sufficient  water  at  constant  pressure 
for  the  demands  of  the  bath  and  a  varying  excess  running 
to  waste  from  an  overflow  at  the  top  of  the  standpipe.  The 
cooling  water  was  drawn  from  the  bottom  of  the  standpipe 

»  Am.  Chem.  Jour.,  38,  175. 


II 

and  an  arrangement  was  connected  to  the  waste  pipe  of  the 
bath  by  which  the  amount  of  water  flowing  could  be  carefully 
gauged. 

The  formation  of  air  cushions  in  the  loops  of  the  pipes 
was  not  overcome  by  mechanical  means  as  it  was  found 
that  by  rushing  water  through  the  cooling  pipes  of  the  bath 
once  a  day,  the  accumulated  air  could  be  completely  swept 
out  and  no  serious  temperature  effects  ensue. 

The  difficulty  of  variation  in  the  temperature  of  the 
cooling  water  was  overcome  by  employing  two  electric  stoves, 
placed  in  tight  iron  cans  which  were  submerged  in  the  water 
of  the  bath.  The  stoves  were  incandescent  electric  light 
bulbs  and  were  under  control  of  a  delicate  mercury  thermostat 
sensitive  to  0.003  of  a  degree  and  specially  designed  to  have 
all  of  its  mercury  below  the  surface  of  the  water  in  the  bath 
and  was  therefore  unaffected  by  any  fluctuation  in  tempera- 
ture of  the  air  above.  When,  however,  the  tap  water  alone 
was  not  sufficient  to  cool  the  bath  to  the  proper  temperature, 
previous  to  entering  the  brass  pipes,  it  was  passed  through 
a  block  tin  coil  surrounded  with  ice  where  it  was  so  cooled 
that  a  small  flow  accomplished  all  the  lowering  of  temperature 
desired.  By  a  suitable  combination  of  the  cooling  of  the 
circulating  tap  water,  at  times  supplemented  by  the  use  of  ice, 
and  the  heating  effects  of  the  regulated  stoves,  temperatures 
within  0.1°  could  be  maintained  during  a  measurement  lasting 
four  or  five  days  regardless  of  the  external  conditions. 

For  convenience  in  cooling  the  sugar  and  other  solutions 
required  in  setting  up  a  cell  to  the  proper  temperatures  and 
also  to  afford  a  place  to  apply  mechanical  pressure  to  the 
cells  and  watch  their  progress  in  the  earlier  stages  of  the 
measurement  without  risk  of  temperature  changes,  a  smaller 
supplementary  bath  was  constructed  utilizing  the  same 
principles. 

EXPERIMENTAL   RESULTS. 

There  follows  in  Tables  I.  to  IX.  a  tabulation  of  the 
results  obtained  in  the  spring  of  1907.  In  these  measure- 
ments the  manometers  were  filled  with  air,  the  temperature 
regulated  by  the  flowing  tap  water  alone,  and  the  hypodermic 
needle  was  not  employed  to  prevent  dilution. 


12 

Table  L 

0.2  Wt.  normal  solution.  Bxp.  No.  i.  Rotation:  (i) 
original,  24°. 9;  (2)  at  conclusion  of  expr.,  24°. 8;  loss,  o°.i  = 
0.40  per  cent.  Manometer:  No.  n;  volume  of  air,  465.94; 
displacement,  o.oi  mm.  Cell  used,  G.  Resistance  of  mem- 
brane, 220,000.  Corrections:  (i)  atmospheric  pressure,  i.oo; 
(2)  liquids  in  manometer,  0.48;  (3)  dilution,  o.oi;  (4)  concen- 
tration, o;  (5)  capillary  depression,  0.02.  Initial  pressure, 
4.19.  Time  of  setting  up  cell,  4.00  P.M.,  May  7,  1907. 


Temperature. 

\rolu.tnc 

Pressure. 

Time. 

Solution.  Manometer, 

air. 

Osmotic.      Gas. 

Difference. 

May  7. 

11.00  P.M. 

14. 

°8 

15- 

°o 

86 

.  ii 

4 

90 

4- 

70 

O.2O 

MayS. 

12.30  P.M. 

15- 

°i 

15- 

°8 

85 

85 

4 

92 

4- 

70 

O.22 

4.00  P.M. 

14- 

°8 

15- 

°3 

85 

85 

4 

92 

4- 

70 

0.22 

May  9. 

12.15  A-M- 

14- 

°9 

15- 

°2 

86 

.06 

A 

.90 

4- 

70 

O.2O 

4.91          4.7O      O.2I 

Loss  in  rotation  corrected  as  inversion. 
Molecular  osmotic  pressure,  24.55. 
Molecular  gas  pressure,  23.50. 
Ratio  of  osmotic  to  gas  pressure,  1.044. 

Table  II. 

0.3  Wt.  normal  solution.  Exp.  No.  i.  Rotation:  (i) 
original,  36°.6;  (2)  at  conclusion  of  expr.,  36°.6;  loss,  o. 
Manometer:  No.  21;  volume  of  air,  477-75;  displacement, 
0.28  mm.  Cell  used,  B.  Resistance  of  membrane,  367,000. 
Corrections:  (i)  atmospheric  pressure,  i.oo;  (2)  liquids  in 
manometer,  0.50;  (3)  dilution,  o;  (4)  concentration,  o;  (5) 
capillary  depression,  0.02.  Initial  pressure,  5.9.  Time  of 
setting  up  cell,  12.30  P.M.,  May  n,  1907. 

Temperature.                                                  Pressure. 
, • .    Volume  . • , 


Time.  Solution.    Manometer,      air.  Osmotic.      Gas.     Difference. 

May  ii. 

8.00P.M.        15.  °i     i6.°6     61.29       7.32       7.05     0.27 

May  12. 
12.00     M.  15.  °I       15.  °I      61.43         7.30         7.05      0.25 

May  13.  - 
9.00A.M.  15. °0      15. °2      61.31         7.30         7.05      0.25 


7-31          7-05       0.26 

Molecular  osmotic  pressure,  24.37. 

Molecular  gas  pressure,  23.50. 

Ratio  of  osmotic  to  gas  pressure,  1.037. 


13 

Table  III. 

0.4  Wt.  normal  solution.  Exp.  No.  i.  Rotation:  (i) 
original,  47°. 8;  (2)  at  conclusion  of  expr.,  47°. 5;  loss,  o°.3  = 
0.62  per  cent.  Manometer:  No.  21;  volume  of  air,  477.75; 
displacement,  0.13  mm.  Cell  used,  G.  Resistance  of  mem- 
brane, 223,000.  Corrections:  (i)  atmospheric  pressure,  i.oo; 
(2)  liquids  in  manometer,  0.52;  (3)  dilution,  0.04;  (4)  concen- 
tration, o;  (5)  capillary  depression,  0.02.  Initial  pressure, 
8.01.  Time  of  setting  up  cell,  4  P.M.,  May  13,  1907. 

Temperature.  Pressure. 


Time.           Solution.   Manometer 

.     volume 
air. 

Osmotic.      Gas. 

Difference. 

May  13. 

11.00  P.M. 

15-  °I 

16. 

°7 

46 

-56 

9 

76 

9 

40 

0 

36 

May  14. 

II.OO  A.M. 

15-  °2 

15- 

°5 

46 

•57 

9 

76 

9 

40 

0. 

36 

5.00  P.M. 

15  -°0 

15 

,°8 

46 

.64 

Q 

•74 

9 

.40 

O 

34 

9.75     9.40   0.35 

Loss  in  rotation  corrected  as  inversion. 
Molecular  osmotic  pressure,  24.38. 
Molecular  gas  pressure,  23.50. 
Ratio  of  osmotic  to  gas  pressure,  1.037. 

Table  IV. 

0.5  Wt.  normal  solution.  Exp.  No.  i.  Rotation:  (i) 
original,  58°. 8;  (2)  at  conclusion  of  expr.,  58°. 2;  loss,  o°.6  = 
1.02  per  cent.  Manometer:  No.  21;  volume  of  air,  477.75; 
displacement,  o.oi  mm.  Cell  used,  D.  Resistance  of  mem- 
brane, 367,000.  Corrections:  (i)  atmospheric  pressure, j°' 99  j . 

(2)  liquids  in  manometer,  0.53;  (3)  dilution,  0.09;  (4)  concen- 
tration, o;  (5)  capillary  depression,  0.02.  Initial  pressure, 
10.27.  Time  of  setting  up  cell,  5.00  P.M.,  May  9,  1907. 

Temperature.  Pressure. 

Volume 


Time.  Solution.   Manometer.        air.  Osmotic.      Gas.     Difference. 

May  9. 

S.ooP.M.        14. °4     i6.°8     37.35       12.26     11.72     0.54 

May  10. 

8.30A.M.        15. °i     i6.°6     37.35       12.26     11.75     0.51 
S.OOP.M.        15. °2     i6.°o     37.45       12.24     11.74     0.50 

12.25     IJ-74     0-51 
Loss  in  rotation  corrected  as  inversion. 
Molecular  osmotic  pressure,  24.50. 
Molecular  gas  pressure,  23.48. 
Ratio  of  osmotic  to  gas  pressure,  1.044. 


Table  V. 

0.6  Wt.  normal  solution.  Exp.  No.  i.  Rotation:  (i) 
original,  69°. 3;  (2)  at  conclusion  of  expr.,  68°. 7;  loss,  o°.6  = 
0.87  per  cent.  Manometer:  No.  21;  volume  of  air,  477.75; 
displacement,  0.09  mm.  Cell  used,  B.  Resistance  of  mem- 
brane, 363,000.  Corrections:  (i)  atmospheric  pressure,  0.99; 
(2)  liquids  in  manometer,  0.54;  (3)  dilution,  0.09;  (4)  concen- 
tration, o;  (5)  capillary  depression,  0.02.  Initial  pressure, 
13.89.  Time  of  setting  up  cell,  3  P.M.,  May  6,  1907. 

Temperature.  Pressure. 

Volume 


Time.           Solution.  Manometer.         air.  Osmotic.      Gas.  Difference. 
May  6. 

n.oo  P.M.        15. °4     i6.°o  31.32  14.73     14.11  0.62 

May  7. 

11.00  A.M.           IS-     O       14.     9  31.37  14.71       14.09  0.62 

4.30P.M.        15.  °o     i6.°2  31.31  14.74     14-09  0.65 


14.73       14.10      0.63 

Loss  in  rotation  corrected  as  inversion. 
Molecular  osmotic  pressure,  24.55. 
Molecluar  gas  pressure,  23.50. 
Ratio  of  osmotic  to  gas  pressure,  1.045. 

Table  VI. 

0.6  Wt.  normal  solution.  Exp.,  No.  2.  Rotation:  (i) 
original,  69°. 3;  (2)  at  conclusion  of  expr.,  68°.8;  loss,  o°.5  = 
0.72  per  cent.  Manometer:  No.  13;  volume  of  air,  435.09; 
displacement,  0.04  mm.  Cell  used,  D.  Resistance  of  mem- 
brane, 219,000.  Corrections:  (i)  atmospheric  pressure,  0.99; 
(2)  liquids  in  manometer,  0.64;  (3)  dilution,  0.07;  (4)  concen- 
tration, o;  (5)  capillary  depression,  0.02.  Initial  pressure, 
12.73.  Time  of  setting  up  cell,  4.00  P.M.,  May  6,  1907. 

Temperature.  Pressure. 

Volume 


Time.  Solution.   Manometer.        air.  Osmotic       Gas.      Difference. 

May  6. 

u.oo  P.M.   15. °4  i6.°o  28.70  14.76  14.11  0.65 

May  7. 

u.oo  A.M.   15. °o  14. °9  28.73  x4-74  J4-09  0.65 

4-00  P.M.  IS- °0       l6.°2       28.65       14.78       14.09      0.69 

14.76    14.09    0.67 
Loss  in  rotation  corrected  as  inversion. 
Molecular  osmotic  pressure,  24.60. 
Molecular  gas  pressure,  23.48. 
Ratio  of  osmotic  to  gas  pressure,  1.048. 


15 

Table  VII. 

0.7  Wt.  normal  solution.  Exp.  No.  i.  Rotation:  (i) 
original,  79°. 2;  (2)  at  conclusion  of  expr.,  78°. 25;  loss,  o°-95  = 
1.2  per  cent.  Manometer:  No.  13;  volume  of  air,  435.09; 
displacement,  0.29  mm.  Cell  used,  D.  Resistance  of  mem- 
brane, 223,000.  Corrections:  (i)  atmospheric  pressure,  i.oo; 
(2)  liquids  in  manometer,  0.65;  (3)  dilution,  0.14;  (4)  concen- 
tration, o;  (5)  capillary  depression,  0.02.  Initial  pressure, 
14.09.  Time  of  setting  up  cell,  4.00  P.M.,  May  13,  1907. 


Temperature. 

Pressure. 

Time. 

Solution. 

Manometer,      air. 

Osmotic.      Gas. 

Difference. 

May  13. 

11.00  P.M. 

15.  °i 

16. 

°7 

24 

.48 

17 

•30 

16 

•45 

0 

•85 

May  14. 

11.00  A.M. 

IS-  °2 

15 

°5 

24 

,46 

17 

•32 

16 

•45 

0 

,87 

5-OO  P.M. 

15.  °o 

IS 

°8 

24 

.48 

17 

•30 

16 

•44 

0 

,86 

17.31     16.45     0-86 
Loss  in  rotation  corrected  as  inversion. 
Molecular  osmotic  pressure,  24.73. 
Molecular  gas  pressure,  23.50. 
Ratio  of  osmotic  to  gas  pressure,  1.052. 

Table  VIII. 

0.8  Wt.  normal  solution.  Exp.  No.  i.  Rotation:  (i) 
original,  89°.o;  (2)  at  conclusion  of  expr.,  87°. 95;  loss,  i°.o5  = 
1.18  per  cent.  Manometer:  No.  13;  volume  of  air,  435.09; 
displacement,  0.07  mm.  Cell  used,  D.  Resistance  of  mem- 
brane, 139,000.  Corrections:  (i)  atmospheric  pressure,  i.oo; 
(2)  liquids  in  manometer,  0.65;  (3)  dilution,  0.16;  (4)  concen- 
tration, o;  (5)  capillary  depression,  0.02.  Initial  pressure, 
13.39.  Time  of  setting  up  cell,  5  P.M.,  April  27,  1907. 

Temperature.  Pressure. 

Volume 


Time.  Solution.  Manometer,      air.  Osmotic.      Gas.  Difference. 
April  28. 

9.00P.M.            15. °0       14. °0       21.44  I9.8l        18.79  1-02 
April  29. 

8.30A.M.        14.  °7     15.  °o     21.43  19.81     18.77  1-04 

5.00P.M.        14. °6     i5.°252i.43  19.81     18.77  1-04 


19.81     18.78     1.03 
Loss  in  rotation  corrected  as  inversion. 
Molecular  osmotic  pressure,  24.76. 
Molecular  gas  pressure,  23.48. 
Ratio  of  osmotic  to  gas  pressure,  1.055. 


16 


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OF  1  i. 

DIVERSITY 

•~r 


The  results  in  the  following  tables  were  obtained  after 
the  completion  of  the  improvements  in  the  temperature 
regulation  of  the  bath  which  have  already  been  described  and 
also  had  the  advantage  of  the  use  of  the  hypodermic  needle 
in  the  opening  of  the  cell.  The  manometers  employed  were 
filled  with  nitrogen  and  their  gas  volumes  recently  determined. 

The  results  of  one  of  the  earlier  measurements  furnish 
such  an  excellent  duplicate  of  a  0.3  cane-sugar  solution  of 
this  series  that  it  was  introduced  for  the  sake  of  comparison 
in  the  tables  to  follow.  This  procedure  was  justified  as  in 
the  measurement  in  question  there  was  no  loss  in  rotation. 


i8 

Table  I. 

o.i  Wt.  normal  solution.  Bxp.  No.  i.  Rotation:  (i)  orig- 
inal, 12°. 7;  (2)  at  conclusion  of  expr.,  12  °. 7;  loss,  o.  Manom- 
eter: No.  9;  volume  of  nitrogen,  433 . 07 ;  displacement,  0.05 
mm.  Cell  used,  G.  Resistance  of  membrane,  535,000.  Cor- 
rections: (i)  atmospheric  pressure,  i.oo;  (2)  liquids  in  manom- 
eter, 0.43;  (3)  dilution,  o;  (4)  concentration,  o;  (5)  capillary 
depression,  0.02.  Initial  pressure,  1.96.  Time  of  setting  up 
cell,  3.00  P.M.,  Apr.  9,  1908. 

Temperature.  Pressure. 


Time.  Solution.  Manometer.        N2-          Osmotic.    Gas.    Difference. 

Apr.  ii. 

3.30P.M.          15°. o     15°. o     143-77     2.47     2.35     0.12 

Apr.  12. 

9.00A.M.         15°.  o     14°.  8     143.25     2.46     2.35     o.i  i 

2.47      2.35      0.12 

Molecular  osmotic  pressure,  24 . 65. 

Molecular  gas  pressure,  23 .  5Q. 

Ratio  of  osmotic  to  gas  pressure,  i  .049. 


Table  II. 

o.i  Wt.  normal  solution.  Exp.  No.  2.  Rotation:  (i)  orig- 
inal, 12°. 7;  (2)  at  conclusion  of  expr.,  12°. 7;  loss,  o.  Manom- 
eter: No.  5;  volume  of  nitrogen,  471.94;  displacement,  o.oi 
mm.  Cell  used,  A3.  Resistance  of  membrane,  28,421.  Cor- 
rections: (i)  atmospheric  pressure,  0.99;  (2)  liquids  in  manom- 
eter, 0.45;  (3)  dilution,  o;  (4)  concentration,  o;  (5)  capillary 
depression,  0.02.  Initial  pressure,  2.13.  Time  of  setting  up 
cell,  4.00  P.M.,  Apr.  28,  1908. 

Temperature.  Pressure. 


Time. 

Solution.  Manometer. 

vuiumc       i  —  • 

Nj.          Osmotic. 

Gas.    Difference. 

Apr.  29. 

IO.OO  P.M. 

15° 

.0 

15° 

.6 

158 

.29 

(2 

.46) 

2 

•35 

Apr.  30. 

8.30  A.M. 

15° 

.0 

15° 

.8 

157 

.27 

2 

.48 

2 

•35 

0.13 

I2.3O  P.M. 

15° 

.0 

15° 

•  4 

157 

.61 

2 

.48 

2 

•35 

0.13 

2.30  P.M. 

15° 

.0 

15° 

.6 

157 

•37 

2 

•49 

2 

•35 

0.14 

2.48   2.35   0.13 

Molecular  osmotic  pressure,  24 . 83. 

Molecular  gas  pressure,  23 . 50. 

Ratio  of  osmotic  to  gas  pressure,  i  .056. 


19 

Table  III. 

0.2  Wt.  normal  solution.  Exp.  No.  i.  Rotation:  (i)  orig- 
inal, 24°. 9;  (2)  at  conclusion  of  expr.,  24°. 8;  loss,  o°.i  =  0.4 
per  cent.  Manometer:  No.  n;  volume  of  nitrogen,  465.94; 
displacement,  o.o i  mm.  Cell  used,  G.  Resistance  of  mem- 
brane, 220,000.  Corrections:  (i)  atmospheric  pressure,  i.oo; 
(2)  liquids  in  manometer,  0.48;  (3)  dilution,  o.oi;  (4)  con- 
centration, o;  (5)  capillary  depression,  0.02.  Initial  pressure, 
4.19.  Time  of  setting  up  cell,  4.00  P.M.,  May  7,  1907. 

Temperature.  Pressure. 

Volume 


Time.  Solution.  Manometer.         N2.        Osmotic.      Gas.    Difference. 

May  7. 

i  i.oo  P.M.         14°.  8     I5°.o      86.11     4.90    4.70    0.20 

May  8. 
12.30  P.M.  15°. I       15°. 8         85.85       4.92       4.70      0.22 

4.00P.M.          14°. 8     15°. 3       85.85     4.92     4.70     0.22 

May  9. 
I2.OO  M.  I4°-9       15°. 2          86.06      4.90      4.70      O.2O 


4.91       4.70      O.2I 

Molecular  osmotic  pressure,  24 . 55. 

Molecular  gas  pressure,  23 . 50. 

Ratio  of  osmotic  to  gas  pressure,  i  .044. 

Table  IV. 

0.2  Wt.  normal  solution.  Kxp.  No.  2.  Rotation:  (i)  orig- 
inal, 25°.o;  (2)  at  conclusion  of  expr.,  25°.o;  loss,  o.  Manom- 
eter: No.  24;  volume  of  nitrogen,  472.58;  displacement,  0.06 
mm.  Cell  used,  B3.  Resistance  of  membrane,  377,000.  Cor- 
rections: (i)  atmospheric  pressure,  i.oo;  (2)  liquids  in  manom- 
eter, 0.54;  (3)  dilution,  o;  (4)  concentration,  o;  (5)  capillary 
depression,  0.02.  Initial  pressure,  4.26.  Time  of  setting  up 
cell,  12.00  M.,  May  3,  1908. 

Temperature.  Pressure. 


Time. 

Solution. 

—  —  •»    vuiuuic    / 

Manometer.        N«z. 

Osmotic. 

Gas.    Difference. 

May  4. 

8.30  A.M. 

15° 

.0 

15° 

.O 

88 

.66 

4 

.89 

4 

70 

0.19 

12.30  P.M. 

15° 

.0 

14° 

•9 

88 

•63 

4 

.89 

4 

,70 

o.  19 

10.00  P.M. 

15° 

.O 

15° 

.0 

88 

•34 

4 

.91 

4 

70 

O.2I 

Mays. 

8.30  A.M. 

15° 

.O 

15° 

.0 

88 

.64 

4 

.89 

4 

,70 

o.  19 

4 . 90     4 . 70     o .  20 
Molecular  osmotic  pressure,  24 . 50. 
Molecular  gas  pressure,  23 . 50. 
Ratio  of  osmotic  to  gas  pressure,  i  .043. 


20 

Table  V. 

0.3  Wt.  normal  solution.  Bxp.  No.  i.  Rotation:  (i)  orig- 
inal, 36°. 6;  (2)  at  conclusion  of  expr.,  36°.6;  loss,  o.  Manom- 
eter: No.  21 ;  volume  of  nitrogen,  477.75;  displacement,  0.28 
mm.  Cell  used,  B.  Resistance  of  membrane,  367,000.  Cor- 
rections: (i)  atmospheric  pressure,  i.oo;  (2)  liquids  in  manom- 
eter, 0.50;  (3)  dilution,  o;  (4)  concentration,  o;  (5)  capillary 
depression,  0.02.  Initial  pressure,  5.9.  Time  of  setting  up 
cell,  12.30  P.M.,  May  n,  1907. 

Temperature.  Pressure. 

Volume     . — 


Time.  Solution.  Manometer.        Ng.         Osmotic.     Gas.    Difference. 

May  ii. 

S.ooP.M.        15°.  i     i6°.6       61.29     7.32     7.05     0.27 

May  12. 

12.00  M.  15°.  i     15°.  i       61.43     7-30     7-05     0.25 

May  13. 
9.00A.M.  15°. O       15°. 2         6I.3I       7.30       7.05       0.25 


7.31       7.05       0.26 

Molecular  osmotic  pressure,  24.37. 

Molecular  gas  pressure,  23 . 50. 

Ratio  of  osmotic  to  gas  pressure,  i  .037. 


Table  VI. 

0.3  Wt.  normal  solution.  Bxp.  No.  2.  Rotation:  (i)  orig- 
inal, 36°. 7;  (2)  at  conclusion  of  expr.,  36°. 7;  loss,  o.  Manom- 
eter: No.  5;  volume  of  nitrogen,  471.94;  displacement,  0.04 
mm.  Cell  used,  B3.  Resistance  of  membrane,  224,000.  Cor- 
rections: (i)  atmospheric  pressure,  0.98;  (2)  liquids  in  manom- 
eter, 0.59;  (3)  dilution,  o;  (4)  concentration,  o;  (5)  capillary 
depression,  0.02.  Initial  pressure,  5.6.  Time  of  setting  up 
cell,  5.00  P.M.,  May  8,  1908. 

Temperature.                                              Pressure. 
, • — >    Volume     . — • , 


Time.  Solution.  Manometer.        N2.         Osmotic.     Gas.    Difference. 

May  9. 

8.30A.M.         15°. o     15°. o      60.97     7.37     7.05     0.32 

May  10. 

i  .OOA.M.         15°. o     15°. i       61.18     7.34     7.05     0.29 

11.00  P.M.  15°. O       15°. 2         6l.IO      7.34      7.05      0.29 

7.35    7-05   0.30 

Molecular  osmotic  pressure,  24 . 50. 

Molecular  gas  pressure,  23 . 50. 

Ratio  of  osmotic  to  gas  pressure,  i .  043. 


21 

Table   VII. 

0.4  Wt.  normal  solution.  Exp.  No.  i.  Rotation:  (i)  orig- 
inal, 47.9;  (2)  at  conclusion  of  expr.,  47°. 9;  loss,  o.  Manom- 
eter: No.  13;  volume  of  nitrogen,  438.84;  displacement,  0.02 
mm.  Cell  used,  B3.  Resistance  of  membrane,  560,000.  Cor- 
rections: (i)  atmospheric  pressure,  i.oo;  (2)  liquids  in  manom- 
eter, 0.6 1 ;  (3)  dilution,  o;  (4)  concentration,  o;  (5)  capillary 
depression,  0.02.  Initial  pressure,  8.17.  Time  of  setting  up 
cell,  4.00  P.M.,  May  16,  1908. 

Temperature.  Pressure. 


Time. 

Solution.  Manometer.        N2.         Osmotic. 

Gas.    Difference. 

May  17. 

12.00  M. 

15°. 

0 

15° 

.8 

42 

.70 

9-77 

9 

.40 

o 

37 

4.00  P.M. 

15° 

i 

15° 

.6 

42 

•63 

9.78 

9 

.40 

0 

38 

I  I.OO  P.M. 

15° 

0 

15° 

.8 

42 

.70 

9-77 

9 

.40 

o 

•37 

May  18. 

4.30  A.M. 

15° 

o 

15° 

.8 

42 

.67 

9-77 

9 

.40 

o 

37 

9-77     9-40     0.37 
Molecular  osmotic  pressure,  24 . 43. 
Molecular  gas  pressure,  23 . 50. 
Ratio  of  osmotic  to  gas  pressure,  i .  039. 

Table  VIII. 

0.4  Wt.  normal  solution.  Exp.  No.  2.  Rotation:  (i)  orig- 
inal, 47°. 9;  (2)  at  conclusion  of  expr.,  47°. 9;  loss,  o.  Manom- 
eter: No.  5;  volume  of  nitrogen,  471.94;  displacement,  o.  Cell 
used,  A3.  Resistance  of  membrane,  70,000.  Corrections:  (i) 
atmospheric  pressure,  i.oo;  (2)  liquids  in  manometer,  0.6 1; 
(3)  dilution,  o;  (4)  concentration,  o;  (5)  capillary  depression, 
0.02.  Initial  pressure,  8.89.  Time  of  setting  up  cell,  4.00 
P.M.,  May  16,  1908. 


Temperature. 

Pressure. 

Time. 

Solution.  Manometer.        N2« 

Osmotic. 

Gas.     Difference. 

May 

17- 

7.00 

A.M. 

15° 

.1 

15° 

.8 

46 

•53 

9 

•77 

9.40 

0-37 

I2.OO 

M. 

15° 

.0 

15° 

.8 

46 

•5i 

9 

78 

9.40 

0.38 

11.00 

P.M. 

15° 

.0 

J5° 

.8 

46 

•52 

9 

•77 

9.40 

0-37 

May 

18. 

4-30 

A.M. 

15° 

.0 

15° 

.8 

46 

.48 

9 

•78 

9.40 

0.38 

9.78    9.40    0.38 
Molecular  osmotic  pressure,  24 . 45. 
Molecular  gas  pressure,  23 . 50. 
Ratio  of  osmotic  to  gas  pressure,  i .  040. 


22 

Table  IX. 

0.5  Wt.  normal  solution.  Exp.  No.  i.  Rotation:  (i)  orig- 
inal, 58°. 7;  (2)  at  conclusion  of  expr.,  58°. 7;  loss, o.  Manom- 
eter: No.  6;  volume  of  nitrogen,  405.34;  displacement,  0.51 
mm.  Cell  used,  A3.  Resistance  of  membrane,  26,000.  Cor- 
rections: (i)  atmospheric  pressure,  i.oo;  (2)  liquids  in  manom- 
eter, 0.61;  (3)  dilution,  o;  (4)  concentration,  o;  (5)  capillary 
depression,  0.02.  Initial  pressure,  10.47.  Time  of  setting  up 
cell,  4.00  P.M.,  Apr.  21,  1908. 

Temperature.  Pressure. 

Volume 


Time.          Solution.  Manometer.      N2.         Osmotic.        Gas.        Difference. 
Apr.  21. 

ii.oo  P.M.    15°. o     15°. 3     32.06   (12.27)    11.75    (0.52) 

Apr.  22. 

9.00A.M.      15°. O       15°. I       32.03       12.29       11.75       0.54 
12.00  M.          15°. O       15°. 2       32.04       12.28       H-75       0-53 

3.00P.M.    15°. o     15°. 4     31-99     12.30     11.75     0.55 

12.29    11.75    0.54 

Molecular  osmotic  pressure,  24 . 58. 

Molecular  gas  pressure,  23 . 50. 

Ratio  of  osmotic  to  gas  pressure,  i  .046. 


Table  X. 

0.5  Wt.  normal  solution.  Exp.  No.  2.  Rotation:  (i)  orig- 
inal, 58°. 7;  (2)  at  conclusion  of  expr.,  58°. 7;  loss,  o.  Manom- 
eter: No.  6;  volume  of  nitrogen,  405.34;  displacement,  0.09 
mm.  Cell  used,  B3.  Resistance  of  membrane,  122,000.  Cor- 
rections: (i)  atmospheric  pressure,  i.oo;  (2)  liquids  in  manom- 
eter, 0.61;  (3)  dilution,  o;  (4)  concentration,  o;  (5)  capillary 
depression,  0.02.  Initial  pressure,  10.19.  Time  of  setting  up 
cell,  4.30  P.M.,  May  12,  1908. 

Temperature.  Pressure. 


Time. 

Solution.  Manometer.      N2. 

Osmotic. 

Gas.     Difference. 

May  13. 

8.30  A.M. 

15° 

.0 

16 

°.o 

32 

.07 

12 

.27 

II 

•75 

0.52 

May  14. 

8.30  A.M. 

15° 

.  i 

16 

°.  i 

31 

99 

12 

30 

II 

•75 

0-55 

3.OO  P.M. 

15° 

.i 

16 

°-3 

32 

02 

12. 

29 

II 

•75 

0.54 

12.29    11.75   0.54 

Molecular  osmotic  pressure,  24.58. 

Molecular  gas  pressure,  23 . 50. 

Ratio  of  osmotic  to  gas  pressure,   i  .046. 


23 

Table  XL 

0.6  Wt.  normal  solution.  Bxp.  No.  i.  Rotation:  (i) 
original,  69°.!;  (2)  at  conclusion  of  expr.,  69°.!;  loss,  o.  Man- 
ometer: No.  21 ;  volume  of  nitrogen,  362.46;  displacement,  0.18 
mm.  Cell  used,  G.  Resistance  of  membrane,  121,000. 
Corrections:  (i)  atmospheric  pressure,  0.99;  (2)  liquids  in  man- 
ometer, 0.50;  (3)  dilution,  o;  (4)  concentration,  o;  (5)  capil- 
lary depression,  0.02.  Initial  pressure,  9.70.  Time  of  set- 
ting up  cell,  4.30  P.M.,  Apr.  22,  1908. 

Temperature.                                             Pressur  «J 
, • -.  Volume • > 


Time.  Solution.  Manometer.     N2.         Osmotic.        Gas.    Difference. 

Apr.  23. 

4.30P.M.       15°.  o     15°.  6     23.56     14.91     14.09     0.82 
9.30  15°. o     15°. 4     23.57     14.91     14.09     0.82 

Apr.  24. 

8.30A.M.       15°. o     15°. 4     23.59     14-90     14-09    0.81 

14.91     14.09    0.82 
Molecular  osmotic  pressure,  24.85. 
Molecular  gas  pressure,  23 . 48. 
Ratio  of  osmotic  to  gas  pressure,  i .  058. 


Table  XII. 

0.6  Wt.  normal  solution.  Exp.  No.  2.  Rotation:  (i)  orig- 
inal, 69°.!;  (2)  at  conclusion  of  expr.,  69°. i;  loss,  o.  Man- 
ometer: No.  9;  volume  of  nitrogen,  433.07;  displacement,  0.07 
mm.  Cell  used,  D.  Resistance  of  membrane,  273,000.  Cor- 
rections: (i)  atmospheric  pressure,  0.99;  (2)  liquids  in  man- 
ometer, 0.58;  (3)  dilution,  o;  (4)  concentration,  o;  (5)  capil- 
lary depression,  0.02.  Initial  pressure,  8.79.  Time  of  set- 
ting up  cell,  4.30  P.M.,  April  22,  1908. 

Temperature.                                            Pressure. 
, • ,  Volume . 


Time.             Solution.  Manometer.        N2.  Osmotic.  Gas.        Difference. 
Apr.  23. 

4. 30  P.M.     15°. o     15°. 6     28.54  J4-79  14-09     0.70 

Apr.  24. 

8.30A.M.     15°. o     15°. 4     28.50  14.82  14.09     0.73 

12. 30  P.M.       15°. O       15°. 6       28.52  14.81  14.09      O.72 


14.81     14.09    0.72 
Molecular  osmotic  pressure,  24 . 68. 
Molecular  gas  pressure,  23.48. 
Ratio  of  osmotic  to  gas  pressure,  i .  05 1 . 


Table  XIII. 

0.7  Wt.  normal  solution.  Exp.  No.  i.  Rotation:  (i)  orig- 
inal, 79°.o;  (2)  at  conclusion  of  expr.,  78°. 9;  loss,  o°.io  = 
0.13  per  cent.  Manometer:  No.  6;  volume  of  nitrogen,  405.34; 
displacement,  0.02  mm.  Cell  used,  A3.  Resistance  of  mem- 
brane, 56,000.  Corrections:  (i)  atmospheric  pressure,  i.oo; 
(2)  liquids  in  manometer,  0.62;  (3)  dilution,  0.02;  (4)  con- 
centration, o;  (5)  capillary  depression,  0.02.  Initial  pressure, 
15.59.  Time  of  setting  up  cell,  3.00  P.M.,  May  20,  1908. 

Temperature.  Pressure. 


Time 

Solution.  Manometer.       N2. 

Osmotic. 

Gas. 

Difference. 

May  21. 

3.00 

P.M. 

15° 

.O 

15°.  8 

22 

.81 

17 

•39 

16 

•44 

0-95 

11.30 

« 

15° 

.0 

i6°.o 

22 

.80 

17 

40 

16 

•44 

0.96 

May  22. 

6.00 

A.M. 

15° 

.0 

i5°-7 

22 

.80 

17 

.40 

16 

•44 

0.96 

10.00 

« 

15° 

.0 

*5°-9 

22 

.80 

17 

40 

16 

•44 

0.96 

17.40     16.44    0.96 
Molecular  osmotic  pressure,  24.86. 
Molecular  gas  pressure,  23.49. 
Ratio  of  osmotic  to  gas  pressure,  i  .058. 

Table  XIV. 

0.7  Wt.  normal  solution.  Exp.  No.  2.  Rotation:  (i)  orig- 
inal, 79°.o;  (2)  at  conclusion  of  expr.,  78°.95;  loss,  o°.o5  = 
0.06  per  cent.  Manometer:  No.  5;  volume  of  nitrogen,  471.94; 
displacement,  o.io  mm.  Cell  used,  B3.  Resistance  of  mem- 
brane, 293,000.  Corrections:  (i)  atmospheric  pressure,  i.oo; 
(2)  liquids  in  manometer,  0.63;  (3)  dilution,  o.oi ;  (4)  concen- 
tration, o;  (5)  capillary  depression,  0.02.  Initial  pressure, 
14.46.  Time  of  setting  up  cell,  3.30  P.M.,  May  20,  1908. 


Temperature. 

Pressure. 

Time. 

Solution.  Manometer.     N2. 

Osmotic. 

Gas.      Difference. 

May  21. 

5.OO  P.M. 

15° 

.0 

16° 

.0 

26 

•65 

17 

•35 

16 

•44 

0.91 

May  22. 

6.00  A.M. 

15° 

.0 

15° 

•  7 

26 

.64 

17 

•35 

16 

•44 

0.91 

IO.OO      " 

15° 

.0 

15° 

•9 

26 

.66 

17 

•34 

16 

•44 

0.90 

17.35    16.44   0.91 

Molecular  osmotic  pressure,  24 . 79. 

Molecular  gas  pressure,  23 . 49. 

Ratio  of  osmotic  to  gas  pressure,  i  .055. 


OF  THE    * 

UNfV£RS!TY 


25 

Table  XV. 

0.8  Wt.  normal  solution.  Exp.  No.  i.  Rotation:  (i)  orig- 
inal, 89°.o5;  (2)  at  conclusion  of  expr.,  88°. 85;  loss,  o°.2  = 
0.22  per  cent.  Manometer:  No.  9;  volume  of  nitrogen,  433.07; 
displacement,  o.n  mm.  Cell  used,  G.  Resistance  of  mem- 
brane, 210,000.  Corrections:  (i)  atmospheric  pressure,  i.o; 
(2)  liquids  in  manometer,  0.60;  (3)  dilution,  0.03;  (4)  con- 
centration, o;  (5)  capillary  depression,  0.02.  Initial  pressure, 
16.19.  Time  of  setting  up  cell,  4.30  P.M.,  May  14,  1908. 

Temperature.  Pressure. 


Time. 

—  '  %      V  ^lUAAlt 

Solution.  Manometer.      Na. 

Osmotic. 

Gas.      Difference. 

May  15. 

5-00  P.M. 

15° 

.0 

15° 

.6 

21 

.18 

20 

.04 

18 

•79 

1-25 

May  16. 

3.30  A.M. 

15° 

.0 

15° 

•4 

21 

.19 

20 

03 

18 

•79 

1.24 

6.30 

15° 

0 

15° 

•4 

21 

,18 

2O. 

04 

18 

•79 

1.25 

20.04 

Molecular  osmotic  pressure,  25.05. 
Molecular  gas  pressure,  23 . 49. 
Ratio  of  osmotic  to  gas  pressure,  i  .067. 


Table  XVI. 

0.8  Wt.  normal  solution.  Exp.  No.  2.  Rotation:  (i)  orig- 
inal, 88°.7;  (2)  at  conclusion  of  expr.,  88°.55;  loss,  o°.i5  = 
0.17  per  cent.  Manometer:  No.  9;  volume  of  nitrogen,  433.07; 
displacement,  0.26  mm.  Cell  used,  D.  Resistance  of  mem- 
brane, 263,000.  Corrections:  (i)  atmospheric  pressure,  0.99; 
(2)  liquids  in  manometer,  0.60;  (3)  dilution,  0.02;  (4)  con- 
centration, o;  (5)  capillary  depression,  0.02.  Initial  pressure, 
13.66.  Time  of  setting  up  cell,  5.00  P.M.,  May  18,  1908. 

Temperature.  Pressure. 


Time. 

Solution.  Manometer,       N2. 

Osmotic. 

Gas.      Difference. 

May  19. 

12.  OO  M. 

15° 

.0 

15° 

.8 

21 

14 

20 

09 

18. 

79 

1.30 

II.OO  P.M. 

15° 

.0 

15° 

.8 

21 

,16 

20 

,07 

18. 

79 

1.28 

May  20. 

II.OO  A.M. 

15° 

.0 

15° 

•7 

21 

,  12 

2O 

II 

18. 

79 

1.32 

20.09    18.79    1-30 
Molecular  osmotic  pressure,  25 .  n. 
Molecular  gas  pressure,  23.49. 
Ratio  of  osmotic  to  gas  pressure,  i  .069. 


26 

Table  XVII. 

0.9  Wt.  normal  solution.  Bxp.  No.  i.  Rotation:  (i)  orig- 
inal, 98°.3;  (2)  at  conclusion  of  expr.,  98°. o;  loss,  o°.3  = 
0.31  per  cent.  Manometer:  No.  15;  volume  of  nitrogen, 
419.63;  displacement,  0.15  mm.  Cell  used,  D.  Resistance 
of  membrane,  112,000.  Corrections:  (i)  atmospheric  pres- 
sure, 0.98;  (2)  liquids  in  manometer,  0.60;  (3)  dilution,  0.05; 
(4)  concentration,  o;  (5)  capillary  depression,  0.02.  Initial 
pressure,  14.39.  Time  of  setting  up  cell,  4.30  P.M.,  May  5, 
1908. 

Temperature.  Pressure. 


Time. 

Solution.  Manometer 

V  uiULLic 

N2. 

Osmotic. 

Gas.        Difference. 

May  6. 

10.00  P.M. 

15° 

.0 

15° 

.0 

18 

.00 

22 

,90 

21 

,14 

I.76 

May8. 

8.30  A.M. 

15° 

.0 

15° 

,0 

17 

•97 

22, 

94 

21  , 

14 

I.  80 

2  .  00  P.M. 

15° 

.0 

15°. 

o 

17 

•99 

22. 

92 

21  , 

•14 

I.78 

22.92     21.14     1.78 
Molecular  osmotic  pressure,  25.47. 
Molecular  gas  pressure,  23.49. 
Ratio  of  osmotic  to  gas  pressure,  i .  084. 

Table  XVIII. 

0.9  Wt.  normal  solution.  Bxp.  No.  2.  Rotation:  (i)  orig- 
inal, 97°. 8;  (2)  at  conclusion  of  expr.,  97°. 65;  loss,  o°.i5  = 
0.15  per  cent.  Manometer:  No.  13;  volume  of  nitrogen,  432.84; 
displacement,  0.13  mm.  Cell  used,  G.  Resistance  of  mem- 
brane, 210,000.  Corrections:  (i)  atmospheric  pressure,  0.99; 
(2)  liquids  in  manometer,  0.64;  (3)  dilution,  0.02;  (4)  con- 
centration, o;  (5)  capillary  depression,  0.02.  Initial  pressure, 
15.21.  Time  of  setting  up  cell,  5.00  P.M.,  May  18,  1908. 


Temperature. 

A  TV*!  11  »>•»«* 

Pressure. 

Time. 

Solution.  Manometer.      N*. 

Osmotic. 

Gas.     Difference. 

May  19. 

4-30 

P.M. 

15° 

.0 

15°.  8 

18 

.64 

22 

.87 

21  . 

14 

i-73 

II  .00 

" 

15° 

.0 

15°.  8 

18 

.60 

22 

.92 

21  . 

14 

1.78 

May  : 

10. 

5-00 

A.M. 

15° 

.0 

15°.  6 

18 

.64 

22 

.87 

21  . 

H 

i-73 

12.  OO 

M. 

15° 

.0 

15°.  7 

18 

.61 

22 

.91 

21  . 

14 

1.77 

22.89     21.14     i-75 
Molecular  osmotic  pressure,  25.43. 
Molecular  gas  pressure,  23 . 49. 
Ratio  of  osmotic  to  gas  pressure,  i  .083. 


27 

Table  XIX. 

i.o  Wt.  normal  solution.  Exp.  No.  i.  Rotation:  (i) 
original,  107°. 5;  (2)  at  conclusion  of  expr.,  107°. 5;  loss,  o. 
Manometer:  No.  9;  volume  of  nitrogen,  433.07;  displacement, 
0.33  mm.  Cell  used,  D.  Resistance  of  membrane,  180,000. 
Corrections:  (i)  atmospheric  pressure,  0.99;  (2)  liquids  in 
manometer,  0.60;  (3)  dilution,  o;  (4)  concentration,  o;  (5) 
capillary  depression,  0.02.  Initial  pressure,  17.88.  Time 
of  setting  up  cell,  4.00  P.M.,  Apr.  30,  1908. 

Temperature.  Pressure. 

Volume 


Time.  Solution.  Manometer.      Nj.  Osmotic.        Gas.     Difference. 
May  i. 

10. 30  P.M.       15°. o     15°. i     16.82  25.38  23.49     J-89 

May  2. 

12. 30  P.M.          15°. O       15°. I       16.82  25.39  23.49       1.90 

n.oo   "  15°. o     14°. 8     16.81  25.41  23.49     J-92 


25-39       23.49       1.90 

Molecular  osmotic  pressure,  25 . 39. 

Molecular  gas  pressure,  23 . 49. 

Ratio  of  osmotic  to  gas  pressure,  i .  080. 


Table  XX. 

i.o  Wt.  normal  solution.  Kxp.  No.  2.  Rotation:  (i)  orig- 
inal, 107°. 5;  (2)  at  conclusion  of  expr.,  107°. 2;  loss,  o°.3  = 
0.28  per  cent.  Manometer:  No.  15 ;  volume  of  nitrogen,  419.63 ; 
displacement,  1.29  mm.  Cell  used,  G.  Resistance  of  mem- 
brane, 180,000.  Corrections:  (i)  atmospheric  pressure,  0.99; 
(2)  liquids  in  manometer,  0.6 1;  (3)  dilution,  0.04;  (4)  con- 
centration, o;  (5)  capillary  depression,  0.02.  Initial  pressure, 
10.55.  Time  of  setting  up  cell,  4.00  P.M.,  Apr.  3,  1908. 

Temperature.  Pressure. 


Time. 

Solution. 

Manometer.        N2. 

Osmotic. 

Gas.      Difference. 

May  2. 

I2.3O  P.M. 

1,5° 

.0 

15°. 

,i 

16 

.28 

2,5 

•39 

23 

•49 

1.90 

5-00      " 

15° 

.0 

15° 

,o 

16 

•27 

25 

.40 

23 

•49 

1.91 

11.00      " 

15° 

.0 

14° 

,8 

16 

.27 

25 

.40 

23 

•49 

1.91 

25.40   23.49    1.91 

Molecular  osmotic  pressure,  25.40. 

Molecular  gas  pressure,  23.49. 

Ratio  of  osmotic  to  gas  pressure,  i .  08 1 . 


28 


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30 

CONCLUSION. 

In  comparing  the  results  (Tables  I.  to  IX.),  in  which  the 
temperature  was  controlled  by  the  running  tap  water  alone, 
we  note  variations  in  temperature  which  seem  large  when 
contrasted  with  those  of  subsequent  measurements.  The 
average  temperature  of  the  bath  was,  however,  15°.!  and  in 
spite  of  these  changes  the  series  is  fairly  satisfactory  for  the 
conditions  under  which  we  were  then  working.  The  mean 
loss  in  rotation  was  0.75%.  Tables  I.-VIII.  give  a  record 
of  the  individual  experiments  and  Table  IX.  a  summary  of  the 
results. 

The  second  series  of  results  (Tables  I.  to  XX.,  Series  2) 
were  obtained  under  more  favorable  circumstances.  There 
is  practically  no  variation  in  temperature  and  the  loss  in  ro- 
tation (Table  XXI.)  is  so  small  as  to  have  little  influence  on  the 
measurements.  A  minimum  point  is  observed  as  previously 
noted  in  the  ratio  of  the  osmotic  to  the  gas  pressures  at  the 
0.4  normal  concentration.  This  may  be  due  to  the  fact  that 
the  o.i,  0.2  and  0.3  normal  concentrations  are  too  low  as  our 
experimental  errors  are  more  evident  in  these  concentrations — 
or  possibly  to  some  other  influences  whose  action  is  at  present 
obscure.  A  comparison  is  furnished  between  results  obtained 
with  manometers  filled  with  air  and  those  containing  nitrogen, 
and  the  conclusion  is  that  manometers  filled  with  air,  provided 
the  gas  volume  has  been  recently  determined,  give  results 
differing  but  little  from  those  in  which  nitrogen  is  employed, 
and,  therefore,  that  the  previous  series  of  measurements 
were  not  appreciably  influenced  by  this  source  of  error. 

Table  XXII.  presents  some  interesting  data.  In  it  are 
given  the  actual  pressures  observed,  uncorrected  for  loss  in 
rotation,  in  the  measurements  at  o°,  5°,  10°,  and  15°,  the 
totals  of  these  pressures  and  the  differences  between  them, 
followed  by  the  molecular  osmotic  pressures  (the  molecular 
osmotic  pressure  is  obtained  by  dividing  the  sum  of  the 
pressure  observed  by  5.5,  the  sum  of  the  concentrations  of 
the  solutions)  and  their  differences.  Also  the  molecular  gas 
pressures  and  differences  and  the  mean  percentage  loss  in  rota- 


tion.  A  comparison  of  the  differences  between  the  molecular 
osmotic  pressures  and  the  corresponding  differences  of  the 
molecular  gas  pressures  brings  out  an  interesting  relationship, 
leaving  out  the  values  of  0.17  and  0.36  between  o°  and  4°  to 
5  °  for  the  reason  that  osmotic  pressure  does  not  seem  to  behave 
normally  in  the  vicinity  of  maximum  density  of  the  solvent, 
and  also  because  in  these  series  the  method  of  measurement 
was  less  refined  than  in  Series  V.  and  VI.  It  is  seen  that  the 
difference  of  0.38  for  the  increase  in  molecular  osmotic  pres- 
sure varies  but  0.06  from  the  corresponding  difference  of  the 
molecular  gas  pressures  between  4°  to  5°  and  10°  and  that 
there  is  even  more  striking  agreement  in  these  differences 
between  10°  and  15°.  Osmotic  pressure  then  seems  to  in- 
crease with  about  the  same  rapidity  as  gas  pressure  between 
these  points;  but  while  these  differences  offer  a  basis  for 
speculation  regarding  the  temperature  coefficient  of  osmotic 
pressure,  we  do  not  feel  justified  in  venturing  any  statement 
as  to  the  laws  governing  the  same  but  have  determined  with 
the  improved  method,  with  its  limited  sources  of  errors,  which 
is  now  available  to  investigate  the  conditions  at  higher  tem- 
peratures and  also  to  redetermine  the  pressures  already 
obtained  which  are  subject  to  any  doubt  because  of  a  higher 
percentage  of  error  at  that  time,  with  the  hope  of  discovering 
if  possible  the  fundamental  principles  governing  the  rise  in 
osmotic  pressure  with  increase  in  temperature. 


The  Development  of  a  New  Cell  for  the 
Measurement  of  Osmotic  Pressure. 


Two  great  obstacles  have  barred  the  way  to  a  more  rapid 
progress  in  the  measurement  of  osmotic  pressure  in  this 
laboratory.  First,  but  less  important,  a  sufficient  supply  of 
accurately  calibrated  manometers  and  second,  the  lack  of  a 
large  number  of  cells  capable  of  giving  trustworthy  measure- 
ments. By  constant  application  the  number  of  manometers 
has  been  increased  and  this  want  somewhat  lessened,  but 
the  lack  of  suitable  cells  is  still  a  serious  problem  and  has 
continued  to  hinder  the  work  up  to  the  present  time;  accord- 
ingly it  was  decided  to  give  this  subject  especial  attention. 

The  cell  now  in  use  presents  several  opportunities  for 
improvement  (for  a  description  see  Am.  Chem.  Jour.,  34,  4). 
In  the  first  place,  it  is  a  difficult  matter  to  prepare  one  for 
the  deposition  of  the  membrane  by  setting  the  glass  tube  and 
soapstone  washer  with  shellac  and  litharge  cement  and  coat- 
ing the  exposed  surfaces  with  rubber  solution  to  furnish  a 
tight  joint.  If  this  connection  has  the  slightest  leak,  no 
matter  with  what  care  the  subsequent  depositing  of  the 
membrane  is  carried  out,  the  cell,  although  of  suitable  texture 
for  measurements,  can  never  develop  maximum  pressure,  and 
considerable  time  is  lost  in  determining  this  fact.  Then,  too, 
if  the  joint  is  of  excellent  character,  in  time  cracks  may  de- 
velop in  the  protecting  rubber  coating,  thus  allowing  the 
sugar  solution  to  corrode  the  litharge  cement  which  necessi- 
tates a  complete  renovation  and  reassembling  of  the  parts  of 
the  cell. 

Another  cause  of  trouble  in  the  present  cell  is  that  the 
glass  tube  is  subject  to  somewhat  rough  treatment  at  the 
time  of  closing  and  opening  the  cell,  and,  in  spite  of  most 


33 

careful  precautions,  is  scratched  or  weakened  and  subsequently 
cracks.  Some  of  our  most  useful  cells  have  unfortunately 
experienced  such  accidents  which  is  a  serious  matter  as  the 
cell,  in  the  process  of  digging  out  the  cements  and  removing 
the  membrane,  is  subject  to  injury  and,  without  accidents,  it 
is  at  least  a  month's  time  before  it  is  in  condition  for  use. 

It  was  also  hoped  to  make  some  improvement  in  the 
method  of  connecting  the  manometer  with  the  cell,  the 
process  at  present  being  time-consuming  and  difficult,  and 
one  subjecting  the  manometers  to  considerable  danger  of 
breaking.  By  reducing  the  time  of  closing  which  often 
extends  over  a  period  of  twenty  minutes,  the  danger  of 
dilution  at  this  point  would  be  avoided.  Then,  too,  after 
the  cell  has  been  closed  by  the  present  method  the  rubber 
stopper  continues  to  give  and  requires  considerable  com- 
pression to  make  a  rigid  joint  and  often  allows  a  slight  rise  of 
the  manometers  in  the  higher  concentrations. 

After  a  consideration  of  these  facts  it  seemed  necessary 
to  abandon  the  glass  connecting  tube  as  it  appeared  to  be  the 
cause  of  much  of  the  difficulty  and  to  construct  a  cell  which 
could  be  connected  with  the  manometer  directly.  On  attack- 
ing the  problem  with  this  end  in  view  the  first  difficulty 
encountered  was  the  impossibility  of  making  a  tight  con- 
nection between  the  membrane  of  the  cell  and  the  rubber 
stoppers  on  the  manometers.  This  is  overcome  in  the  present 
cell  by  allowing  the  membrane  to  form  a  connection  with  the 
permanent  rubber  coating  on  the  inside  of  the  cell  which,  as 
it  is  never  disturbed,  is  quite  satisfactory.  It  became  evident 
that  some  such  arrangement  must  still  be  employed,  but 
that  the  rubber  coating  lacking  the  durability  required 
was  unsuitable  for  the  purpose.  It  was  decided  to  glaze  that 
part  of  the  cell  which  comes  in  contact  with  the  manometer 
and  allow  this  glaze  to  extend  into  the  cell  where  the  mem- 
brane could  form  a  connection  with  it  much  the  same  as  in 
the  present  form.  The  problem  then  was  to  obtain  a  suitable 
glaze,  and  the  usual  difficulties  were  experienced,  most  of 
the  glazes  obtainable  showing  a  tendency  to  craze.  By  a 
careful  study  of  the  problem  and  numerous  experiments,  a 


34 

glaze  with  the  proper  coefficient  of  expansion  was  obtained 
and  has  proved  quite  satisfactory. 

The  next  question  was  to  devise  a  means  of  connecting  the 
manometer  with  the  cell  which  should  not  only  be  rapid  in 
execution,  but  also  furnish  a  joint  capable  of  withstanding 
great  pressures  without  leaking,  and  allow  for  the  application 
of  the  required  mechanical  pressure  on  the  enclosed  sugar 
solutions.  Several  forms  were  planned  and  constructed, 
each  of  which  in  turn  proved  unsatisfactory  but  furnished 
additional  knowledge  of  the  necessary  requirements  which 
at  length  seems  to  have  led  to  success.  The  familiar  principle 
of  the  taper  joint  combined  with  a  rubber  packing  is  employed 
and  a  diagram  of  the  most  successful  form  is  shown  in  the 
accompanying  cut. 

DESCRIPTION   OF   THE   CELL. 

The  cell  A  is  composed  of  the  same  material  as  those  in 
use  at  present  and  is  glazed  from  the  top  down  to  the  line 
shown  at  i,  both  inside  and  out.  From  this  line  on,  the 
wall  remains  porous  and  is  suitable  for  the  deposition  of 
the  membrane.  The  neck  of  the  cell  is  constricted  and  tapers 
slightly  from  the  outside  to  the  interior.  B  represents  a 
portion  of  the  manometer  which  passes  through  the  nut  at  b 
and  enters  the  conical  brass  plug  shown  at  e  which  is  turned 
to  the  same  taper  as  the  neck  of  the  cell  and  bored-out  at 
the  top  for  reception  of  a  setting  of  Wood's  metal  shown  at  d 
which  holds  the  manometer  rigidly  in  place.  This  joint  is 
made  more  secure  by  an  enlargement  of  the  manometer  tube 
and  a  depression  cut  in  the  interior  of  the  brass  plug  which 
will  be  easily  understood  by  a  glance  at  the  diagram.  The 
use  of  Wood's  metal  as  a  setting  material,  after  unsuccessful 
experimentation  with  various  sealing  waxes  and  cements, 
has  given  excellent  results.  It  melts  easily,  thus  removing 
danger  of  cracking  the  manometers,  sets  quickly  and  rigidly 
and  expands  on  cooling — three  very  desirable  features. 
The  rubber  packing  designated  by  /  is  slipped  on  the  conical 
plug  and  tied  securely  to  the  manometer  at  its  lower  end  with 
"waxedend."  This  rubber,  if  of  proper  quality  and  thickness, 


35 

should  furnish  a  tight  joint  with  the  cell  and  prevent  the 
sugar  solution  from  coming  in  contact  with  the  brass  plug. 
The  question  of  obtaining  a  suitable  texture  of  rubber  for 
this  joint  has  been  a  troublesome  one  and  has  not  as  yet  been 
settled  to  our  satisfaction.  The  rubber  must  be  soft  and 
yielding  and  at  the  same  time  tough  enough  to  withstand  a 
tearing  strain  and  the  withdrawal  of  the  needle  without 
rupture  or  cutting.  The  brass  nut  shown  at  b  is  slotted  in 
such  a  way  that  it  can  easily  be  slipped  on  to  the  manometer. 
A  part  of  its  lower  portion  is  cut  out  to  receive  the  top  of  the 
conical  brass  plug  and  tends  to  hold  it  in  position.  This  nut 
is  threaded  into  the  brass  collar  at  c  which  in  turn  grips  the 
cell  at  g  where  a  lead  washer  is  employed  to  prevent  injury 
to  the  outside  of  the  cell. 

The  act  of  closing  is  carried  out  as  follows:  After  rilling 
the  cell  with  sugar  solution,  the  manometer,  properly  fitted 
with  the  brass  plug  and  rubber  washer,  is  forced  into  the  neck 
of  the  cell  along  with  a  hypodermic  needle  which  connects 
the  interior  of  the  cell  with  the  air,  passing  between  the  rubber 
packing  and  the  cell  wall  and  out  through  the  slot  in  the  nut. 
The  collar  is  slipped  on  the  cell  from  below,  and  the  nut  placed 
on  the  top  of  the  brass  plug  is  turned  on  the  threads  of  the 
collar  till  the  proper  pressure  is  exerted  on  the  rubber  pack- 
ing, the  needle  meanwhile  allowing  the  excess  of  sugar  solution 
caused  by  the  advance  of  the  manometer  into  the  cell  to 
escape.  The  needle  is  withdrawn  and  as  there  is  now  no 
communication  of  the  interior  of  the  cell  with  the  air,  on  turn- 
ing the  nut  any  desired  pressure  can  be  obtained  and  the 
rubber  packing  made  more  effective. 

The  opening  is  even  a  more  simple  process.  The  nut 
is  unscrewed,  the  rubber  packing  pierced  with  the  hypodermic 
needle  and  the  manometer  quickly  withdrawn. 

It  is  evident  that  this  cell  has  some  advantages  over  the 
present  form.  It  is  simple  in  construction  and  is  ready  for 
the  removal  of  air  and  the  deposition  of  the  membrane  after 
the  firing  of  the  glaze.  This  permits  a  more  rapid  weeding 
out  of  poor  cells.  Tha  size  of  the  membrane  can  easily  be 
regulated  as  the  interior  of  the  cell  can  be  glazed  to  any 


36 

desired  point,  and  if  too  small  a  portion  seems  to  have  been 
reserved,  some  of  the  glaze  can  be  easily  removed  with  a 
carborundum  wheel  and  the  porous  area  increased. 

The  cell  can  be  quickly  closed  and  opened  requiring 
about  two  minutes  for  the  closing  and  a  minute  for  the  opening, 
while  the  present  cell  requires  about  fifteen  and  three  minutes 
respectively.  In  the  operation  of  opening  and  closing  no 
diminished  pressure  is  exerted  and  therefore  no  dilution 
arises  from  this  cause.  It  is  also  impossible  for  the  manom- 
eter to  rise  because  of  its  rigid  setting.  There  are  no  glass 
tubes  to  break,  no  rubber  coating  to  disintegrate  and  no 
cements  subject  to  corrosion. 

A  number  of  quantitative  measurements  have  been  satis- 
factorily completed  with  this  cell  and  some  of  the  results  are 
given  in  the  tables  above.  It  is  our  hope  that  on  continued 
use  it  will  satisfactorily  perform  the  function  it  was  designed 
to  fulfil  and  be  of  great  service  in  the  subsequent  measuring 
of  osmotic  pressure. 


BIOGRAPHICAL. 

Brainerd  Hears  was  born  at  Amherst,  Massachusetts, 
January  17,  1881.  His  early  training  was  received  at  Drury 
Academy,  North  Adams,  Mass.  He  entered  Williams  College 
in  September,  1899,  and  graduated  from  that  institution  with 
the  B.  A.  degree  in  1903  and  with  the  M.  A.  degree  in  1905. 
He  was  assistant  in  chemistry  in  Williams  College  for  three 
years  after  graduation.  In  October,  1906,  he  entered  the 
Johns  Hopkins  University  as  a  graduate  student  in  chemistry, 
his  subordinate  subjects  being  physical  chemistry  and  geology. 


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